1. Field of the Invention
This invention relates to the preparation of tetrahydrofuran and gamma-butyrolactone from at least one of maleic anhydride or succinic anhydride. In one embodiment this invention relates to a single stage process for the vapor phase hydrogenation of maleic anhydride or succinic anhydride in the presence of a catalyst comprising the mixed oxides of copper, zinc and aluminum to produce high yields of tetrahydrofuran. In another embodiment, this invention relates to a single stage process for the vapor phase hydrogenation of maleic anhydride or succinic anhydride in the presence of a catalyst comprising the mixed oxides of copper, zinc and aluminum to produce high yields of tetrahydrofuran and gamma-butyrolactone.
2. Description of the Prior Art
Tetrahydrofuran is a useful solvent for natural and synthetic resins and is a valuable intermediate in the manufacture of a number of chemicals and plastics. Gamma-butyrolactone is an intermediate for the synthesis of butyric acid compounds, polyvinylpyrrolidone and methionine. Gamma-butyrolactone is a useful solvent for acrylate and styrene polymers and also a useful ingredient of paint removers and textile assistants.
It is known in the art that tetrahydrofuran and gamma-butyrolactone may be produced by a number of different methods. For example, tetrahydrofuran is produced by the dehydration of 1,4-butanediol and gamma-butyrolactone can be prepared by the dehydrogenation of 1,4-butanediol. Specifically, most tetrahydrofuran and gamma-butyrolactone is manufactured in a multi-step sequence starting with the reaction of acetylene and formaldehyde in the presence of a cuprous acetylide complex to form butynediol. The butynediol is reduced to butanediol, which is dehydrated to tetrahydrofuran and dehydrogenated to gamma-butyrolactone as indicated above.
In addition, tetrahydrofuran and gamma-butyrolactone can be prepared by catalytic hydrogenation of maleic acid, fumaric acid and succinic acid, their respective anhydrides and ester derivatives.
The instant invention focuses on the production of tetrahydrofuran and tetrahydrofuran with gamma-butyrolactone from maleic anhydride. A multi-step process for producing tetrahydrofuran and gamma-butyrolactone in addition to 1,4-butanediol from maleic anhydride is described in U.S. Pat. No. 4,584,419. In this patent the ethyl diester of maleic anhydride is produced and then hydrogenated in the presence of a copper-chromite catalyst to yield minor quantities of tetrahydrofuran and larger quantities of 1,4-butanediol and gamma-butyrolactone.
Tetrahydrofuran and gamma-butyrolactone are derived from maleic anhydride or succinic anhydride using nickel base catalysts in U.S. Pat. No. 3,853,922 and U.S. Pat. No. 3,829,448.
Lastly, U.S. Pat. No. 3,894,054 describes a vapor phase process for the conversion of maleic anhydride to tetrahydrofuran using a two component catalyst system consisting of a Cu/Zn/Cr catalyst and a silica-alumina catalyst which had been calcined at approximately 1000.degree. C.
An object of this invention is to provide a process for producing tetrahydrofuran and optionally gamma-butyrolactone from maleic anhydride and succinic anhydride in high yields using a single component catalyst and without first esterifying the anhydride. Another object is to provide an efficient catalyst which will produce tetrahydrofuran and optionally gamma-butyrolactone in high yields in a single hydrogenation step with less by-products. Still another object is to provide a novel hydrogenation catalyst which maintains high activity over time.